Engine Cooling and Heating Systems
Engine Cooling
Process by which heat is removedRadiation, convection and conduction35% of total engine heat is removed by the cooling system
Cooling System Functions
Carries heat that is produced by the engine combustion process away from the engineHelps the engine to reach normal operating temperature fasterMaintains a constant temperature throughout the engine
Cooling System Functions
Picks up engine heat through conduction and carries it to the radiator where it is released to the atmosphere through convectionKeeps system under pressure to raise the boiling point and prevent liquid lose from evaporation
Coolant Flow
Standard FlowCoolant is drawn from the bottom of the radiator into the engineFlows through the water jackets in the block and up to the cylinder headFlows from the cylinder head out the thermostat and back into the top of the radiator
Coolant Flow
Reverse FlowCoolant is drawn from the bottom of the radiator into the engineThe water pump directs coolant through the water jackets in the cylinder head and down into the blockFlows from the block out the thermostat and back into the top of the radiator
Radiators
Components
TanksCoreFinsOil Cooler
Radiator Construction
TanksConstructed from copper, brass, aluminum or plasticCollects the coolant and transfers it through the tubes to be cooledReceiving tank contains baffles to help direct the coolant evenly over the tubesMay include an internal tank for automatic transmission fluid cooling
Radiator Construction
CoreTubes or fins made of copper or aluminumFins are thin sheets of metal that are soldered together to form channels for the coolant to pass through between the tanksMost are only a few thousandths of an inch thick
Radiator Construction
Core (cont)Tubes are either soldered or crimped to the tankThe number of cores is equal to the rows of tubes or fins (2 core, 3 core, 4 core etc.)
Radiator Construction
FinsIncrease air movement across the core to remove heat faster from the tubes
Oil CoolerCirculates hot transmission fluid through tubes surrounded by cooler engine coolant
Radiator Designs
Down-FlowCoolant moves vertically through the tubes or finsTypical of standard-flow systems moving from top to bottomBased on the principle that heat rises pushing hot coolant to the top and allowing cooler fluid to flow to the bottom (early systems w/o water pump)
Radiator Designs
Cross-FlowCoolant moves horizontally through the tubes or finsCommon on late model vehicles in both standard and reverse-flow systemsWorks well w/ modern low hood designsMore efficient cooling due to longer tubes (allows air movement over the tubes for a longer period of time)
Coolant Flow
Radiators
Radiator Failure
Leaks in the core from physical abuse
Radiator Failure
Leaks in the core from corrosion or electrolysis
Radiator Failure
Leaks between the core and the tank
Radiator Failure
Cracked or damagedtank
Radiator Failure
Leaking transmission cooler inside the tank
Radiator Failure
Damaged Fins
Radiator Failure
Plugged fins from foreign media
Radiator Failure
Plugged tubes from corrosion build-up
Pressurized Cooling System
Maintained by cap Pressure is determined by the cap’s rating15-17 psi gasoline engine7 psi dieselExcess pressure is allowed to enter the recovery (overflow) tank
During cool downVacuum created in the radiatorValve in the cap allows coolant to flow back from the recovery tank
Radiator Cap
APressureRelease
BVacuumCool-down
Coolant Recovery System
Recovery/overflow tankUnder atmospheric pressureStores expanded hot fluid Releases stored fluid back into the radiator during vacuum cool down
Coolant Recovery System
Expansion tankSealed and pressurized with the pressure capPurges air from the cooling systemMay have a bleeder valve
Coolant Recovery System
Air BleedLocated in a high part of the cooling systemUsed to purge air from the system when filling w/ new coolant
Radiator ServiceVisually inspect for leaks and external damage of radiator and recovery tankVisually inspect for corrosion build-up in radiator corePressure test to check for leaks
Radiator Service
Pressure test and inspect cap Inspect sealing surface of cap on the radiator neck for nicks or damageA failed cap can cause lose of coolant, overheating, collapsed hoses and component failure due to excessive pressure build-up
Radiator Service
Inspect shroud for damage and proper mounting
A fan shroud can increase cooling by 30%A failed or improperly mounted fan shroud can cause overheating and/or damage to the radiator core
Radiator Service
System BleedingAll air must be bled from the system after refilling with coolantMany systems include an air bleedMay have to loosen a hose at the highest point in the system to release all the air (heater hose)
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